A light emitting diode (LED) is an optical semiconductor device that emits a light when voltage is applied. The LED is widely used in a variety of electronic products, electronic display boards such as instrument panels, and the like with various colors including red, green, blue, yellow, etc.
Among these, an LED electronic bulletin board is configured such that a number of LEDs are arranged in the form of a matrix thereon to form pixels so that an image can be displayed. Such an LED electronic bulletin board is installed and used in various forms on the exterior or interior of a building so as to deliver advertisements or various items of information.
Typically, the LED electronic bulletin board receives a video signal from an audio/video (AV) device such as a DVD player, a VCR player, broadcasting equipment, or the like, and converts the received video signal into an appropriate signal so that an image is displayed on the electronic bulletin board. A number of LEDs or small fluorescent tubes are arranged in the form of a matrix on the LED electronic bulletin board to display various items of information such as various kinds of characters or pictures.
The LED electronic bulletin board is a display device that implements a color image with excellent resolution and various colors, and is installed and used in various forms on the external wall or the interior of a building to deliver advertisement or broadcasting services to implement an image or a moving picture. The LED electronic bulletin board includes, as a basic constituent element, a unit pixel consisting of light emitting diodes (LEDs) that emit red (R), green (G), and blue (B) colors, and pixels are arranged in the form of a matrix of horizontal rows and vertical columns to constitute one LED panel or LED board.
The LED electronic bulletin board can supply data corresponding to each of points of an image to an associated one of the pixels to implement various colors through the control of the brightness of the LEDs of red, green and blue colors, and also implement an image with various colors over the LED electronic bulletin board. The resolution of a screen that can be implemented by the LED electronic bulletin board of a given area is determined by the number of pixels within a unit area. Thus, as the size of the pixel is decreased, the resolution of the LED electronic bulletin board can be increased. Nevertheless, there is a limitation in reducing the size of the pixel to a predetermined size due to a limitation of a manufacture process or technique.
In addition, as shown in FIGS. 1 and 2, a general electronic bulletin board is configured such that it is controlled by signals CLK and LATCH through the drive of a constant current driving LED via a main controller unit (MCU) and a sub controller unit (SCU), data read from a memory is stored in a shift register of an LED constant current driver IC, and image data is processed by a data input/output driving method of outputting the image data to a color-dependent LED according to each data when an OE (Output Enable) output control signal is asserted,
In the meantime, a conventional electronic bulletin board is operated by a separate device and driving algorithm for brightness calibration according to each electronic bulletin board depending on the expression mode, the expression dot, and the entire size of the electronic bulletin board. The conventional electronic bulletin board is operated by a driving algorithm necessary separately depending on a module- and dot-dependent brightness calibration value of electronic bulletin boards, leading to a restriction in compatibility between the electronic bulletin boards, which results in unnecessary additional installation of a device.
Therefore, there is a proposal for a technology in which module- and dot-dependent brightness calibration of electronic bulletin boards is enabled, and the brightness of the LED electronic bulletin board can be conveniently calibrated irrespective of a pixel or brightness value of the LED electronic bulletin board.